System of ship propulsion.



W. L. R. EMMET.

SYSTEM OF SHIP PROPULSION.

APPLICATION FILED' AUG. 21. 191 1.

1,176,668. Patented Mar. 21, 1916.

I 3 SHEETSSHEET l.

Fig.1.

THE COLUMBIA PLANOGnAPH 20., WASHINGTON, n. c.

W. L. R. EMMET.

SYSTEM OF SHIP PROPULSION.

APPLICATION FILED AUG-21.1911.

1, 176,668. Patented Mar. 21, 1916.

I 3 SHEETS-i-SHEET 2- Fig. 2.

Witnesses: Inventor:

' William LREmmeL,

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His aqttornea THE COLUMBIA YPLANDGRAPH v61).. WASHINGTON. D c.

W. L. R. EMMET.

SYSTEM OF SHIP PROPULSION.

APPLICATION FILED AUG.21, 191x.

1 1 76,668. Patented Mar. 21, 1916.

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Witnesses: Inventor":

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UNITED STATES PATENT onr cn.

WILLIAM I. R. EMMET, OF SCHENEOTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF SHIP PROPULSION.

Specification of Letters Patent.

Patented Mar. 21, 1916.

Application filed August 21, 1911. Serial N 0. 645,175.

To all whom, it may concern:

Be it known that I, WILLIAM L. R. EMMET, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Systems of ShipPropulsion, of which the following is a specification.

This invention relates to systems of ship propulsion by electricity andhas for its object the provision of a system of such a character that alarge amount of electric energy in the form of heat is capable of beingdissipated in a rapid and eificient manner through the agency of anysuitable supply of water, such as sea water.

In my previous application, Serial No. 529,577, I have described andclaimed an electrical system of ship propulsion embodying the use ofelectric generators and motors. In systems of this character it isnecessary to employ electrical resistances which at times-becomeexcessively hot. This is especially true'upon the reversals of themotor, although the arrangement may be such that the resistance is incircuit and becomes hot at other times.

One of the objects ofmy invention is to provide such a .system in whichprovision is made for dissipating th1s excessive heat energy inathoroughly safe and rehable manner. In my- Patent No. 1,062,900, May

27, 1913, I have described and claimed a resistance suitable for thepurpose above described.

My present invention relates more specifically to a system of shippropulsion embodying resistances cooled by circulating water.

In the accompanying drawing illustrat ing my system of ship propulsion,Figure 1 is a section through the hull of a ship showing the propellershafts and the water cooled resistances; Fig. 2 is an enlarged view ofthe water cooled resistance connected to the side of a ship; and Fig. 3illustrates the general arrangement of the parts of the system and thecircuit connections.

Referring first to Fig. 3, it will be seen that my system involves theuse of a generator G driven by a steam turbine T. The

particular type of turbine forms no part of my invention, and forpurposes of illustration I have shown one in a conventional way havlng avalve B for controlling the admis- S1011 of steam and an exhaust pipe X.This turbine is direct connected to the generator G which is excitedfrom the direct current supply circuit D. The generator which I haveshown is of thethree phase type and supplles current to the electricmotor M; A reversing'swit'ch S is provided for reversing the directionof rotation of the motor. This motor I have illustrated as aninductionmotor having an external resistance R arranged to be connected incircuit with its rotor through slip rings on the shaft. The

resistance is either connected in circuit or short circuited by shiftingthe operating lever L. The motor is direct connected to the propellershaft upon which the propeller P is mounted. In the operationof thissystem the resistance R will be short circuited during normal operation;that is, when the ship is running either ahead or astern. When thepropeller is to be reversed, however, especially if the reversal is tobe sudden, a powerful torque must be exerted by the motor to overcomethe inertia of the ship. In order to accomplish this the resistance R isthrown into the rotor circuit. The result is that a heavycurrenttraverses this resistance so as to heat the resistance. In order toincrease the current which this resistance can safely carry, I providemeans for carrying oil the heat developed in the resistance. Inaccomplishing this result, I make use of any available supply ofcirculating water, such as the sea water, and cause it to circulate overthe resistance. After extracting the heat/from the resistance elementthe water may be caused to return overboard.

In order that the resistance element may be cooled most eifectively, itis essential that the water shall be in direct contact with theresistance element. In providing a resistance which is to be cooled inthis way, difiiculties terminals, which not only tends to eat away theconductor at the points where the current flows into the surroundingwater but also gives a continuously varying resistance due to theformation of air bubbles and steam at these points. In my previousapplication above referred to, I have disclosed a water cooledresistance which is satisfactory for this purpose. In Fig. 2 of thepresent drawings I have shown such a resistance arranged to be cooled bythe circulation of sea water from the side of the ship.

Referring now to Fig. 2, it will be seen that the water cooled rheostatis connected to the side of the ship through an intake valve 10 and anoutlet valve 11. The rheostat is arranged for a three phase systemalthough it is obvious that my invention is in no sense limited to thisparticular application. As thus arranged for a three phase system, therheostat consists of two headers or mani folds 12 and 13, the formerbeing connected with the intake valve and the latter with the outletvalve. Between these two headers are connected three casings l4, l5 and16, one for each resistance. The construction of these three casings isthe same, as is also the arrangement of the resistance within thecasings. Each has a lower enlarged portion 17 of insulating material,and an upper contracted portion 18 of similar material. These twosections are secured together, as shown, so as to form a continuous ductor conduit. Tie rods 19 are connected between the two headers so as tostrengthen the structure and feet 20 are supplied upon the lower headerfor supporting the rheostat upon the floor. In the lower enlargedportion of each duct is a resistance conductor 21 consisting of aplurality of resistance spirals connected together so as to permit thefree circulation of the water between the turns of the spiral and alsobetween the various spirals. The particular material which I employ forthis purpose has a high resistance and may be safely run at a hightemperature. Furthermore, it will not oxidize or corrode. For thispurpose the resistance material described and claimed in the patent toDempster, 901,428, is well suited. I have found this material to bealmost entirely non-corrosive and to successfully withstand longsubmersion in salt solution. It is furthermore very slightly affected byelectrolysis. The resistance material is preferably made in the form ofa flat ribbon and wound into a spiral, as shown. The spirals arearranged transversely of the casing so that the flat side of theconductor is parallel with the sides of the casing. This arrangementreduces the resistance to the flow of water and leaves no place for theaccumulation of bub bles. These successive spirals are connectedalternately at their inner and outer ends so as to make the windingsnon-inductive. The

resistance element extends only through the enlarged portion of thecasing and the upper portion is provided in order to increase the lengthof the path through which the electric current can leak through thewater. In 7 order to further increase the resistance of the path theupper part of the casing is reduced in size, as above described. The upper casing is reduced in size by an amount approximately suiiicient tocompensate for the space in the larger casing occupied by the resistanceelement so that the reduction causes no great impediment to the flow ofwater. By this arrangement a large amount of electric energy can bedissipated in a very small space. As above stated, in the normaloperation of my system this rheostat will not be in use. When, however,it is desired to reverse, the ship, say, for instance, from full speedahead to full speed astern, the rheostat is connected in circuit withthe rotor of the motor. The resistance is so designed that under thesecircumstances it will heat rapidly and a circulation of the water whichis in the conduits will take place due to the heating of the water inthe lower section of the conduit. Cold water will therefore be taken inthrough the intake valve and the hot water will be discharged throughthe outlet valve 11. By this means a very large amount of heat energymay be dissipated in a very short time, while the space occupied, whichis necessarily limited on shipboard, is reduced to a minimum. Thisarrangement makes it possible to reverse the propellers in a veryeffective manner without danger of overheating.

While I have described my invention as embodied in concrete form forpurposes of illustration it should be understood that I do not limit myinvention thereto, since various modifications thereof will suggestthemselves to.those skilled in the art with out departing from thespirit of my invention, the scope of which is set forth in the annexedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. In a system of electric ship propulsion, an alternating currentgenerating unit, a propeller driving induction motor electricallyconnected to said generating unit, a resistance adapted to beelectrically included in the secondary circuit of said motor, aninsulating duct surrounding said resistance, and an intake pipe and adischarge pipe connected to said duct and communicating with the wateroutside the ship and arranged so that the heat generated in theresistance effects a circulation of water through said duct.

2. In a system of electric ship propulsion, a polyphase alternatingcurrent generating unit, a propeller driving polyphase induction motorelectrically connected to said generating unit, a plurality ofinsulating ducts, an intake pipe and a discharge pipe connected to saidducts and communicating With the Water outside the ship, and aresistance adapted to be electrically included in the circuit of eachphase of the secondary Winding of said motor, each resistance beingarranged in one of said ducts and adapted to effect by the heatgenerated therein a circulation of water through said duct.

In Witness whereof, I have hereunto set my hand this 19th day of August,1911.

' WILLIAM L. R. EMMET. Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

Copies of this patent may be obtained for live cents each, by addressingthe Commissioner of Patents, Washington, D. C.

